Page 135 - Microtectonics

124 5 · Shear Zones

Fig. 5.11. Striped gneiss composed of alternating layers of recrystallised feldspar and quartz ribbons. Some of the quartz ribbons contain
strongly elongated single crystals, probably formed by grain boundary migration within the ribbon. Section parallel to the aggregate
lineation and normal to the foliation. Três Rios, Rio de Janeiro State, Brazil. Width of view 2.3 mm. CPL

Fig. 5.12. K-feldspar porphyroclast with undulose extinction. A mantle of recrystallised feldspar with isolated polycrystalline quartz
ribbons surrounds the porphyroclast. Notice the strongly elongated single crystals of quartz in the ribbons. Section parallel to the
aggregate lineation and normal to the foliation. Três Rios, Rio de Janeiro State, Brazil. Width of view 10 mm. CPL